Electric Charges and their Conservation

Correct answer: B. Negative

Explanation: The governing concept is charging by friction, in which electrons—not protons—are transferred between different materials. Ebonite has a greater tendency to attract and retain electrons than wool. Thus electrons move from the wool to the ebonite; the rod gains excess negative charge. Positive charge would mean electron loss, while neutral or zero charge would ignore the transfer.

Correct answer: A. Positive

Explanation: Charging by friction involves transfer of electrons between the two materials. In the usual ebonite–wool interaction, electrons move from wool to ebonite because ebonite attracts them more strongly. Wool therefore loses electrons and is left with an electron deficiency, which is represented as positive charge. It does not become negative, neutral, or charge-free after this transfer.

Correct answer: B. Charging by conduction

Explanation: The defining feature of charging by conduction is direct contact. When a charged body touches a neutral conductor, mobile charges move between them until electrical equilibrium is approached, so the neutral conductor acquires charge of the appropriate sign. Friction charges materials through rubbing, whereas induction uses a nearby charged body without contact. Magnetization concerns magnetic properties, not electric charge transfer.

Correct answer: C. Induction

Explanation: Charging by induction occurs without direct contact. A charged object is brought near a conductor, causing the conductor’s mobile charges to separate or rearrange under electrostatic influence. With suitable earthing and removal of the external body, the conductor can retain a net charge. Conduction requires touching, friction requires rubbing, and heating alone is not the defining charging method here.

Correct answer: A. Free charges can move easily in it

Explanation: A conductor contains charge carriers that can move comparatively freely through the material. In metals, these carriers are mainly delocalized electrons, while the positive ions remain in a lattice. Because mobile charges respond to an electric field, conductors allow charge redistribution and current. A conductor need not be neutral or permanently positive or negative, so the other choices confuse conductivity with net charge.

Correct answer: A. Free electrons

Explanation: In a metallic solid, atoms contribute valence electrons that become delocalized throughout the lattice. These free electrons acquire a small drift velocity when an electric field is applied, producing conventional electric current. Protons and atomic nuclei are bound in the lattice and cannot freely cross it, while neutrons carry no electric charge. Therefore free electrons are the principal carriers of conduction in metals.

Correct answer: A. Remains constant

Explanation: The governing law is conservation of electric charge. Charge may move from one body to another, but in an isolated system no net charge enters or leaves the system. If the initial charges are q1 and q2, the total is Q = q1 + q2; after transfer, q1' + q2' remains equal to Q. Transfer changes individual charges, not their total sum.

Correct answer: A. Same magnitude and opposite sign

Explanation: The elementary charge has magnitude e ≈ 1.602 × 10⁻¹⁹ C. A proton carries +e, while an electron carries −e. Hence their charge magnitudes are equal, but their signs are opposite. The electron is not neutral, does not have twice the proton’s charge, and does not share the same sign. This comparison follows the basic definition of positive and negative elementary charge.

Correct answer: A. Because it has magnitude and sign only

Explanation: A scalar quantity is described by magnitude, while a vector additionally requires a spatial direction. Electric charge is specified by its magnitude and algebraic sign, positive or negative; the sign is not a direction in space. Charges can be added algebraically, such as +2 C + (−1 C) = +1 C. Therefore charge is scalar, not a north-directed, always-zero, or velocity-dependent quantity.

Correct answer: B. Negatively charged

Explanation: Electric charge is determined by the algebraic sum of proton and electron charges. Protons contribute positive charge, while electrons contribute negative charge. If the number of electrons exceeds the number of protons, the negative contribution is larger, so the net charge is negative. Therefore option B is correct; equal numbers would give neutrality, while excess protons would produce positive charge.

Correct answer: B. Positively charged

Explanation: A proton has positive charge and an electron has negative charge of equal elementary magnitude. When the positive contribution from protons is greater than the negative contribution from electrons, the algebraic sum of charge is positive. Hence option B is correct. Neutrality requires equal positive and negative contributions, not a proton excess.

Correct answer: A. Their total charge is still zero

Explanation: The conservation of electric charge states that charge cannot be created or destroyed in an isolated system. During rubbing, electrons are transferred between the two bodies: one loses electrons and becomes positive, while the other gains them and becomes negative. The charges are equal in magnitude and opposite in sign, so their combined charge remains zero. Option A is correct.

Correct answer: A. Earthing

Explanation: Earthing, or grounding, is the process of connecting a conductor to the Earth through a conducting path. Because Earth is an enormous charge reservoir, electrons can flow between the conductor and Earth until the conductor reaches a suitable potential, often approximately zero potential. Thus option A is correct; friction charges by rubbing, induction rearranges charge, and polarization separates bound charges.

Correct answer: A. Into Earth

Explanation: When a charged conductor is connected to Earth, excess electrons can flow between the conductor and the ground because a potential difference drives the movement. For a negatively charged conductor, excess electrons generally flow into Earth; for a positively charged conductor, electrons may flow from Earth to it. In the situation described as excess charge being removed, option A is correct. Charge is transferred, not destroyed.

Correct answer: A. Isolated system

Explanation: For an isolated system, no net electric charge crosses the system boundary. Therefore, although charges may separate or move internally, the algebraic sum of all charges remains constant: Q_total, final = Q_total, initial. This is the simple form of the conservation law. Option A is correct. An open system can exchange charge with its surroundings, so its internal total need not remain constant.

Correct answer: D. Being a vector with direction

Explanation: Electric charge is a scalar physical quantity, so it has magnitude and sign but no independent spatial direction. It is conserved in an isolated system, quantized according to q = ne, and additive because the total charge equals the algebraic sum of individual charges. Therefore being a vector is not a property, making option D correct. The other three are standard properties of charge.

Correct answer: A. Gain or loss of electrons

Explanation: In ordinary charging processes, the nucleus remains bound inside the atom, so protons do not normally leave the body. Electrons, especially outer electrons, can be transferred by friction, conduction, or induction-related processes. Gaining electrons makes an object negative and losing electrons makes it positive. Thus option A is correct; the other choices do not describe ordinary charging.

Correct answer: B. They will repel each other

Explanation: Coulomb’s law describes the electric force between two point charges, with magnitude proportional to |q₁q₂|/r². The force is repulsive when q₁q₂ is positive, which occurs for two positive charges. Therefore option B is correct: they push away from each other. Attraction occurs for opposite signs, while neutrality is not produced merely by bringing two like charges near one another.

Correct answer: B. They will attract

Explanation: According to Coulomb’s law, the sign of q₁q₂ determines whether the electric force is attractive or repulsive. A positive charge and a negative charge have opposite signs, so q₁q₂ is negative and the force is attractive. Thus option B is correct: the charges tend to move toward each other if free to move. Like charges repel, and attraction does not change either particle’s mass to zero.

Correct answer: B. Repulsive force

Explanation: The governing concept is the interaction between electric charges: like charges repel and unlike charges attract. Since the two bodies have charges with the same sign, Coulomb’s law gives a repulsive force along the line joining them. Therefore the smaller body is pushed away from the nearby body, making option B correct. Option A applies to opposite signs, while C is not an electric-force category and D ignores the charge interaction.

Correct answer: A. Net charge is zero

Explanation: The governing concept is net charge, which is the algebraic sum of all positive and negative charges in a body. In a neutral body, positive and negative charges balance, so the net charge is zero. In elementary usage, an uncharged body likewise has no resultant charge and is assigned zero net charge. Thus option A is correct; B and C indicate an excess of one sign, and D has no physical meaning here.

Correct answer: A. Positive charge effect is greater than negative charge effect

Explanation: Net charge is found by adding charges algebraically, with positive and negative signs retained. A positive result means the total positive contribution exceeds the total negative contribution. In an ordinary solid this commonly results from a deficit of electrons, not from the disappearance of all particles. Therefore option A is correct. Option B describes a negative net charge, C describes neutrality, and D is unrelated to charge.

Correct answer: A. Negative charge effect is greater than positive charge effect

Explanation: The sign of net charge is determined by the algebraic sum of all charges. A negative result means that the negative contribution exceeds the positive contribution. For ordinary matter, this usually means that the body has gained extra electrons, while the positive nuclei remain part of the material. Hence option A is correct. Option B represents positive charge, C represents neutrality, and D incorrectly confuses a negative sign with destruction of charge.

Correct answer: A. Sudden creation or destruction of total charge in an isolated system

Explanation: The conservation law states that the algebraic total charge of an isolated system remains constant. Charge may move from one object to another, such as electrons transferring during rubbing, but the system’s total charge does not suddenly appear or disappear. Therefore option A correctly describes what the law prevents. Option B is allowed by conservation, while C and D are forces or interactions, not prohibited processes.

Correct answer: A. Charges in the paper become rearranged

Explanation: The governing concept is electrostatic induction or polarization. A charged comb produces an electric field that slightly shifts the bound charges in each neutral paper piece. The side nearer the comb acquires an induced charge of opposite sign, and the attractive force at the shorter distance is stronger than the repulsive force on the farther side. Thus the net force is toward the comb, making A correct; the other choices are false.